1. Field of the Invention
The present invention relates to an electronic apparatus of the liquid-cooled type, in which a heat-generating component such as a CPU is cooled with liquid coolant. More particularly, the invention relates to a structure of a circulation path of the liquid coolant.
2. Description of the Related Art
A CPU is incorporated in, for example, notebook-type portable computers. The heat that the CPU generates while operating is increasing as its data-processing speed rises, and it performs more and more functions. The higher the temperature of the CPU, the less efficiently it operates. To cool the CPU, so-called cooling systems of the liquid-cooling type have been developed in recent years. A liquid-cooling system uses a liquid coolant that has a far higher specific heat than air.
Japanese Patent Application KOKAI Publication No. 7-142886 discloses a cooling system of the liquid-cooling type, configured for use in portable computers. The cooling system comprises a heat-receiving header, a heat-radiating header, and a tube for circulating the coolant. The heat-receiving header is provided in the housing of a portable computer and thermally connected to the CPU incorporated in the housing. The heat-radiating header is provided in the display unit of the portable computer. The tube extends from the housing to the display unit of the portable computer. It connects the heat-receiving header and the heat-radiating header. Liquid coolant is circulated between the heat-receiving header and the heat-radiating header.
In this cooling system, the liquid coolant in the heat-receiving header absorbs the heat generated by the CPU. That is, the coolant is heated in the heat-receiving header. The coolant thus heated is transferred via the tube into the heat-radiating header. The heat-radiating header radiates the heat generated by the CPU, as the coolant flows through it. The coolant is therefore cooled in the heat-radiating header. The coolant thus cooled is transferred via the tube, back into the heat-receiving header through the tube. Back in the heat-receiving header, the coolant again absorbs the heat from the CPU. As the coolant is thus circulated, the heat is transmitted from the CPU to the heat-radiating header with high efficiency and the heat-radiating head radiates the heat. This cooling enhances the efficiency of cooling the CPU.
In the conventional cooling system, the tube through which the liquid coolant flows extends between the housing and display unit of the computer. The display unit is coupled to the housing and can rotate. To allow the display unit to rotate smoothly, the tube is made of synthetic resin having sufficient flexibility. Since the tube is made of synthetic resin, the liquid coolant inevitably leaks, and passes through the tube and eventually evaporates. To reduce the wasting of the coolant due to its evaporation outside the tube, it is desirable to make the tube as short as possible.
In the conventional cooling system, however, the tube coupled to the heat-receiving header meanders, passing around various functional components provided in the housing of the computer. The tube is therefore very long. Consequently, the liquid coolant evaporates from the tube in large quantities. The coolant liquid must be replenished or replaced with fresh coolant very frequently. The maintenance of the cooling system requires much labor and time. If the coolant is not replenished, the efficiency of cooling the CPU will decrease to impair the reliability of the cooling system.